1. Field of the Invention
The present invention relates to an in-tank return line filter element. Specifically, the present invention relates to an in-tank return line filter elements and hydraulic reservoirs that incorporate the respective filter elements.
2. Background Information
Hydraulic reservoirs are used to hold hydraulic fluid that can be utilized by hydraulic systems, such as used in heavy machinery, including cranes, backhoes, demolition shears, bulldozers, and the like. In hydraulic systems, it is important to keep the hydraulic fluid free of debris. Consequently, filter units or filter assemblies have been incorporated in the hydraulic systems to filter debris from the hydraulic fluid.
U.S. Pat. Nos. 6,116,454; 6,475,380 and 6,508,271 disclose hydraulic reservoir designs that incorporate specific filter assemblies therein (i.e. in-tank filter elements), and these patents are incorporated herein by reference. The filter elements can be on the outlet lines, as shown in the '454 patent or in the inlet lines as shown in the '380 and '271 patents. A filter element on the outlet or suction side of a hydraulic reservoir is generally a simple strainer. Placing the filter element in the inlet or return lines that extends to the reservoir, as shown in the '271 and '380 patents provides certain advantages relating to the energy required by filtration and returning of the fluid to the reservoir.
The large majority of in-tank filter elements for hydraulic reservoirs utilize a return line filter element of some kind. One known or common example is a forming a partition or separate box structure within the hydraulic reservoir and incorporating a top mounted, or drop-in, filter element therein. A similar known configuration is to have the filter element as part of a larger filter assembly which is “dropped” into the top of the container with the return lines connected directly to the head of the filter assembly. This filter element is also a top mounted structure. The term “top mounted” refers to access or mounting direction in that the filter element is accessed and replaced through the top of the reservoir, such as in the '271 patent. These prior art top mounted filter elements result in a large amount of components and design complexity in the filter assembly due to sealing requirements and the like that are necessary.
There is a need in the industry for a simple, efficient, in-tank, in-line filter element for a return line of a hydraulic reservoir.